1. Field of the Invention
The present invention relates to a structure for controlling the capacity of a variable displacement compressor comprising a swash plate, accommodated in a control pressure chamber, rotatable together with a rotary shaft and variable in inclination angle relative to the rotary shaft and a plurality of pistons, arranged around the rotary shaft and subject to a reciprocating motion corresponding to the inclination angle of the swash plate, wherein the inclination angle of the swash plate is controlled by regulating the pressure in the control pressure chamber.
2. Description of the Related Art
In a variable displacement compressor of the type disclosed in Japanese Unexamined Patent Publication (Kokai) No. 10-246181, as the pressure in a crank chamber (the control pressure chamber referred to in this text) becomes higher, the inclination angle of the swash plate becomes smaller to reduce the discharge capacity, while as the pressure in the crank chamber becomes lower, the inclination angle of the swash plate becomes larger to increase the discharge capacity. In a variable displacement compressor of this type which is capable of controlling the capacity in accordance with the pressure in the crank chamber, the maximum inclination angle of the swash plate is defined by interrupting the inclination of the swash plate by a rotary support which rotates together with the rotary shaft and supports the swash plate via a hinge mechanism.
The swash plate is made of aluminum for the purpose of weight reduction, which has a drawback in that direct contact of a rotary support, made of iron, with the swash plate made of aluminum causes wear of a contact portion of the swash plate. If the contact portion of the swash plate is worn, the maximum inclination angle of the swash plate may be changed. To solve such a problem, according to the compressor disclosed in Japanese Unexamined Patent Publication (Kokai) 10-246181, an iron weight is attached to the swash plate so that direct contact is made between the iron weight and the rotary support. Wear of the swash plate is avoided by this arrangement of direct contact between iron members whereby the maximum inclination angle of the swash plate is prevented from changing.
A pair of restriction bosses are formed integral with the rotary support to be in contact with the weight. The hinge mechanism consists of a pair of support arms formed on the rotary support side and a single guide pin secured on the swash plate side wherein opposite ends of the guide pin engage into guide holes of the respective support arms. Accordingly, when the swash plate is at the maximum inclination, this maximum inclination angle is maintained in a stable state by four contact portions; i.e., those between the pair of guide holes and the guide pin and between the pair of restriction bosses and the weight. The positions at which the pair of restriction bosses are brought into contact with the weight are symmetrical on the circumference of the swash plate about the top dead center as seen in the axial direction of the drive shaft. That is, one of the contact positions between the pair of restriction boss and the weight is contained in a discharge stroke zone on the swash plate about the rotary shaft as seen in the axial direction of the drive shaft, while the other of the contact positions between the pair of the restriction boss and the weight is contained in a suction stroke zone on the swash plate about the drive shaft as seen in the axial direction of the drive shaft. The discharge stroke zone is defined as a region of the swash plate which advances the piston from the bottom dead center side toward the top dead center side as the swash plate rotates to discharge refrigerant gas from the compression chamber. The suction stroke zone is defined as another region of the swash plate which returns the piston from the top dead center side toward the bottom dead center side as the swash plate rotates to suck the refrigerant gas into the compression chamber. As a result, a discharge reaction generated as the refrigerant gas is discharged from the compression chamber is accepted by the rotary support via the contact portions of the restriction bosses in contact with the weight within the discharge stroke zone, as seen in the axial direction of the drive shaft, and the hinge mechanism. Accordingly, the positions of the restriction bosses to be in contact with the weight within the discharge stroke zone as seen in axial direction of the drive shaft substantially define the maximum inclination angle of the swash plate. On the contrary, the positions of the restriction bosses in contact with the weight within the suction stroke zone as seen in the axial direction of the drive shaft do not substantially relate to the definition of the maximum inclination angle of the swash plate. In other words, it is useless to provide the restriction bosses within the suction stroke zone as seen in the axial direction of the drive shaft.